Clamp the centrifuge to the edge of a table so that the crank can turn freely.  Place objects of equal mass in each cup.  Spin as desired. 

To simulate the spin cycle of a washing machine, wet two of the small towels, put a ball in the center of each, and inset a towel into each ring on the centrifuge.  Wet the towels throughly, and then spin the centrifuge.  Put a towel on the floor to capture most of the water, and make sure you put on a lab coat before doing the demo.